In subsea operations, hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing geologic formation. Subsea equipment is positioned at the well and may comprise a wellhead and a blowout preventer. A riser may be deployed between the subsea equipment and a surface facility, e.g. a surface vessel. A subsea landing string system may be deployed down through the riser and into the subsea equipment to provide hydraulic controls over various tools and safety features. For example, the subsea landing string system may comprise a subsea control module which actuates directional control valves based on control signals sent from the surface.
The directional control valves are part of an electro-hydraulic system and may be solenoid piloted according to control signals. Based on the control signals, the directional control valves are actuated so as to direct hydraulic actuating fluid to appropriate tools or other features. The solenoids and directional control valves are housed in manifolds mounted inside a dielectric fluid compensated enclosure to prevent exposure to seawater which can cause shorting of the solenoids. Due to the compensated enclosure, large compensators are used which tends to make the overall subsea landing string system larger in size. The compensated enclosure also prevents direct access to the directional control valves which increases the difficulty of servicing and troubleshooting the subsea landing string system. Additionally, the dielectric fluid compensated enclosure and corresponding compensators are vacuum filled which can increase the time involved with both assembly and service of the subsea landing string system.